CDC on Trail of Vaccine for New Bird Flu

As the number of cases of a novel bird flu rises in China, the CDC is taking early steps toward a vaccine.

by Michael Smith Michael Smith North American Correspondent, MedPage Today
April 05, 2013

As the number of cases of a novel bird flu rises in China, the CDC is taking early steps toward a vaccine.

The agency said it is monitoring the situation in China and developing a seed strain for a vaccine – one of the "routine preparedness measures taken whenever a new novel influenza virus is detected in humans."

"This is an evolving situation and there is still much to learn," the CDC said on its website.

But actually getting a vaccine into the clinic is a long process – the candidate vaccine virus must be created, tested in animals, and then sent to drug manufacturers to be grown in large quantities in chicken eggs.

During the H1N1 pandemic in 2009/2010, for instance, it took nearly 3 months from the characterization of the seed strains to the end of the first clinical trial of the new vaccine.

And whether a vaccine against the avian H7N9 influenza strain can be developed quickly remains to be seen.

The official number of cases reported to the World Health Organization so far is 11, with five deaths, but news reports from China put the total at 14 with six fatalities.

There is still no evidence of human-to-human transmission, the WHO said – more than 400 close contacts of the victims are being closely watched and none have become ill.

There is also no evidence of epidemiological links among the victims, who are all from the densely populated provinces on China's eastern seaboard, the agency said.

It's also not clear where the virus is coming from – its reservoir in the animal kingdom – although "intensified investigations" are underway, according to the WHO.

So it's possible the virus has found a home (as other avian flu strains have) in pigs. Indeed, officials in Shanghai -- home to many of the victims – have been dealing with a large number of dead pigs found in the Huangpu River.

But testing of some of the dead animals found no sign of the flu, according to news reports from China.

Another possible source is poultry. The virus has been detected in live pigeons being sold for meat in a Shanghai market; authorities in the city closed the market and slaughtered the birds.

But it's going to be difficult to track an avian zoonotic caused by the H7N9 virus -- unlike the highly pathogenic H5N1 avian flu, H7N9 does not cause illness and death in birds.

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